Lead in guide assembly

ABSTRACT

A lead-in guide assembly is shown for centralizing a downhole tool being run from a well surface within a well bore to a selected downhole location. The lead-in guide can be utilized as a seal assembly guide including a seal carrier provided with a leading end and a trailing end which is made up in a tubing string leading to the well surface. A collapsible guide is located at the leading end of the seal carrier for centralizing the seal carrier within the surrounding cased well bore as the seal assembly is being run into position above a cooperating sealing bore located at a downhole location. The guide means moves to a retracted position as the assembly moves within the cooperating sealing bore.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to downhole tools run within asubterranean well bore from the well surface during the drilling,completion and production of oil and gas wells and, more specifically,to an improved mechanism for protecting the component parts of suchtools during the running-in of such tools to a selected depth within thewell bore.

2. Description of the Prior Art

A large number of downhole tools are used in the oil and gas industrieswhich must be lowered from the well surface to a selected locationwithin the well bore. Many of these downhole tools have component partswhich are fragile, or which otherwise need protection from scraping,jarring or otherwise impacting the surrounding cased or uncased wellbore during the running-in operation. For example, commonly useddownhole tools which require the provision of a seal in the annular arealocated between a fluid transmission conduit, or other tubing string,and a surrounding conduit such as the outer well casing. Such tools maybe employed in the drilling and completion of the well, the productionof the well, the servicing of the well, or the closing-in of a well.Conventional packers utilize an anchoring system which holds a sealingelement in position against other upwardly or downwardly acting pressuredifferentials in order to establish such an annular seal. Suchconventional packers typically employ radially extendible gripping slipsystems and radially expandable packing or sealing elements to preventfluid communication and to provide pressure integrity. Such packers aretypically run-in to position within the well bore and set either on atubing string or on a wireline setting tool. Those packers which are seton a tubing string are typically set using hydraulic pressure within thetubing, hydrostatic pressure in the well bore, or a combination of both.Such packers may also be mechanically set by the application of theforce or weight to the tubing string. Permanent packers of the abovetype include an internal seal bore for receiving tubing which can beretrieved while leaving the packer in place. Retrievable packers utilizesuch techniques as rotation of the tubing string to release the grippingslip assemblies and packing elements for retrieval of the packingelement.

During the above described operations, it is generally necessary thatsealing integrity be established between separate elements within thetubing string or between accessory items and the tubing string. Thus, itis generally necessary where a tubing section is inserted into the sealbore of the packer to establish sealing integrity between that sectionand the packer. One means of providing such sealing integrity is toutilize stacks of sealing elements in which individual sealing elementshave a generally chevron-shaped cross-section. Such sealing systemsemploying chevron-shaped sealing elements are shown, for example on page62 of the 1990 Baker Service Tools Catalog. These chevron-shaped sealingelements and systems are commonly referred to as tieback accessories ortubing seal systems and are generally employed to establish a sealbetween a tubing mounted element and the internal seal bore of aconventional packer.

Another method for providing sealing integrity in the tubing casingannulus and to isolate the production zone from portions of the annulusextending above the packing element is to utilize a polished seal borereceptacle in conjunction with sealing elements. Such a seal assembly isagain shown on page 62 of the Baker Service Tools 1990 Catalog as the"PBR Tieback Seal Assembly." Such sealing assemblies used in conjunctionwith polished seal bore receptacles provide a tubing to casing annularseal and permit isolation of the production zone from the tubing-casingannulus. These assemblies can be positioned precisely at a desiredlocation in the casing and permit tubing movement which may resultduring a production or treating cycle.

There are other advantages associated with the use of seal assemblies ofthe above type as compared to conventional radially expanding packingelements. Thus, the sealing function can be achieved with across-sectional area or gap across which the sealing elements mustbridge being much less than that encountered with conventional packingelements. Significant radial expansion of the sealing elements is notrequired. Also, whereas conventional radially expanding packing elementsrequire a more complicated means of expanding the packing element intosealing relationship, the elements of the tubing seal systems areenergized by the pressure which they contain. Thus, they do not need amechanism to expand them or retain them in sealing relationship.

One problem associated with the use of existing tubing seal assembliesinvolves damage to the seal means carried on the tubular seal carrierduring the running-in operation from the well surface into the polishedseal bore receptacle located at the downhole location. The prior artassemblies have not utilized a centralizing device other than a top,stationary gauge ring. Such designs exposed the seals, whethermetal-to-metal or elastomeric, to mechanical damage while running intoposition within the well bore.

The present invention has as its object to provide an improved mechanismfor protecting downhole tools during the running-in of such tools fromthe well surface to a selected downhole location within the well bore orfor preventing the premature actuation of such tools during therunning-in operation.

In one preferred embodiment, the present invention has as its object toprovide a lead-in guide for centralizing a seal assembly being run froma well surface within a well bore to a cooperating sealing bore locatedat a downhole location.

Another object of the invention is to provide a seal assembly guide forcentralizing a packoff seal assembly being run from a well surfacewithin a cased well bore to a cooperating casing or receptacle defininga polished bore surface located at a downhole location.

SUMMARY OF THE INVENTION

The lead-in guide assembly of the invention is used to centralize adownhole tool being run from a well surface to a selected downholelocation. The lead-in guide includes a tubular carrier having aninterior and having an exterior surface defined between a leading endand a trailing end thereof. The trailing end is adapted to be made up ina tubing string leading to the well surface. The tubular carrier alsohas fragile components on the exterior surface thereof. Collapsibleguide means are located in the leading end of the tubular carrier forcentralizing the carrier within the surrounding well bore as the tubularcarrier is being lowered from the well surface. The guide means collapseonce the desired depth is reached within the well bore.

In one embodiment of the invention, the lead-in guide centralizes theleading end of a seal assembly being run from a well surface within awell bore to a cooperating sealing bore located at a downhole location.The guide assembly includes a tubular seal carrier having abutting meansfor locating the seal carrier at the desired depth within thecooperating sealing bore and has external seal means for establishingsealing integrity with the cooperating sealing bore. The tubular sealcarrier has a leading end and a trailing end which is adapted to be madeup in a tubing string leading to the well surface. A collapsible guidemeans is located at the leading end of the tubular seal carrier forcentralizing the seal carrier within the surrounding well bore. Theguide means is collapsible between an expanded, running-in positionwhile above the sealing bore and a retracted position within thecooperating sealing bore.

Preferably, the lead-in guide assembly is used to centralize a packoffseal assembly being run from a well surface within a cased well bore toa cooperating sealing bore receptacle defining a polished seal boresurface located at the downhole location. The tubular seal carrier ofthe assembly has a downwardly facing shoulder for locating the sealcarrier with respect to a cooperable upwardly facing shoulder on thesealing bore receptacle. The seal carrier has external seal means forestablishing sealing integrity with the polished seal bore surface. Thetubular seal carrier has a leading end and has a trailing end adapted tobe made up in the tubing string leading to the well surface. Collapsibleguide means are located at the leading end of the tubular seal carrierfor centralizing the seal carrier within the surrounding cased well boreas the tubular seal carrier is being lowered from the well surface. Theguide means is collapsible between an expanded, running-in positionwhile above the sealing bore receptacle and a retracted position withinthe polished seal bore surface.

The collapsible guide means can comprise a plurality of radiallymoveable guide dogs which are located at the leading end of the tubularseal carrier within window openings provided therein. The guide dogs areradially shiftable between the expanded and retracted positions uponaxial movement of the tubular seal carrier within the polished seal boresurface of the sealing bore receptacle. The guide dogs are selectivelysized to be closely received within the surrounding cased well bore withat least selected guide dogs making contact with the surrounding casedwell bore during the running-in operation in order to centralize thedownhole tool within the cased well bore. The dogs are moved to theretracted position upon contact with the upwardly facing shoulder on thesealing bore receptacle.

Additional objects, features and advantages will be apparent in thewritten description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of one embodiment the lead-in guide assembly of theinvention including a quarter-sectional view of the tubular seal carrierbeing lowered within a surrounding well bore and illustrating the closefit between the seal means thereon and the well casing;

FIG. 2 is an isolated view of the leading end of the tubular sealcarrier showing the guide dogs in the expanded position as the lead-inguide assembly moves through the cased well bore and prior to contactingthe upwardly facing shoulder of the sealing bore receptacle; and

FIG. 3 is a view similar to FIG. 2 showing the movement of the guidedogs to the retracted position as the leading end of the tubular sealcarrier passes within the polished seal bore surface of the sealing borereceptacle.

DETAILED DESCRIPTION OF THE INVENTION

The lead-in guide assembly of the invention can be used with anydownhole tool having fragile components on an extended surface thereofThe term "fragile" for purposes of the present discussion, is meant toencompass not only elastomeric sealing components, but also actuatingmechanisms, and the like, which could be prematurely actuated by contactwith the surrounding well bore or casing during the running-inoperation. A varietyof downhole tools compatible with the lead-in guideassembly of the invention will be readily apparent to those skilled inthe relevant art. For example, in the case of subsea tubing hangers, thehanger must be guided through the blow out preventer and well head. Withvarious hanger and slip gripping mechanisms used in completion andproduction equipment, the latch mechanism or gripping mechanism canbenefit from being protectedfrom impact with the surrounding wellcasing, thereby preventing premature setting.

For ease of explanation, the present invention will be illustrated as aseal assembly guide. FIG. 1 shows a seal assembly guide designatedgenerally as 11. The seal assembly guide 11 is used to isolate anannular area, such as area 13 between an oil well casing 15 and a tubingstring orfluid transmission conduit and the production zone (not shown).The seal assembly guide 11 includes an internally threaded upper extent17 for connection in a tubing string leading to the well surface. Theannular area extends above the production zone and isolation is providedby means of the interaction between a polished seal bore receptacle 19which comprises an integral part of the casing, and a seal means 21which in this case is an elastomeric element which circumscribes atubular seal carrier 23. In the embodiment shown, there are actuallythree sets of sealmeans 21, 25, 27 which are axially spaced along thecarrier 23. The tubularseal carrier 23 has a generally open internalbore 29 for the transmission of fluids and communicates by means of thetubing string connected to the threaded extent 17 with the well surface.The tubular seal carrier 23 includes an upper gauge ring 31 with anabutting shoulder 33 for locating the seal carrier at a desired depthwithin a cooperating sealing bore suchas the polished seal borereceptacle 19. The gauge ring 31 comprises a trailing end of the tubularseal carrier.

The polished seal bore receptacle 19 is typically incorporated into thecasing string 15 when the casing is first installed in a subterraneanoil or gas well. Producing zones would be identified prior toinstallation of the casing 15 and the polished seal bore receptacle 19installed just above a producing zone. The receptacle 19 is attached tothe casing by a threaded connection. Similar threaded connectionslocated at the lower endof the polished seal bore receptacle provideattachment to those portions of the casing extending below thereceptacle. An upwardly facing shoulder 35 is located on the innersurface of the receptacle and is referred to asa no-go shoulder. Thedownwardly facing shoulder 33 serves to locate the tubular seal carrier23 within the receptacle. The inner diameter of the polished seal bore19 is less than the normal inner diameter of the well casing 15.However, this reduction in the diameter of the casing need not be largeand would not appreciably change the cross-sectional area of the casing.

At the point at which it becomes desirable to isolate the productionzones from the casing by preventing communication of produced fluidsbetween theproduction zones and the tubing casing annulus, the sealassembly guide of the invention would be inserted into the well on thelower end of a production string (not shown). The seal carrier 23 islowered until the downwardly facing shoulder 33 encounters the upwardlyfacing shoulder 35 of the receptacle. The seal means 21, 25, 27 are, inthe embodiment shown,seal stacks which comprise a plurality ofchevron-shaped sealing elements.

Although various conventional sealing assemblies could be employed withthis invention, the particular sealing elements depicted comprise aprimary elastomeric sealing member to provide adequate sealing integrityin the presence of high pressure differentials. Such elastomeric sealingelements are known which, for example, utilize a perfluoroelastomer,such as the elastomer commonly referred to under the Dupont trademark"KALRAZ."Each of the seal means, in addition to the elastomeric element39 also includes relatively rigid backup rings of such material aspolyphenylene sulfide, commonly referred to under the Phillips PetroleumCorporation trademark "RYTON" and members formed ofpolytetrafluoroethylene with glassfiller material interspersed therein,commonly referred to as glass filled "TEFLON" a trademark of DupontCorporation. The chevron-shaped sealing assemblies do not require theapplication of mechanical compressive force in order to energize thesealing elements and such chevron-shaped members generally have a smallradial width. Metal backup rings 41, 43 are also shown between adjacentseal assemblies.

Although the preferred embodiment of FIG. 1 includes at least oneelastomeric ring circumscribing the exterior of the tubular seal carrier23, it will be understood that other tubing seal means such asmetal-to-metal seals can be provided circumscribing the exterior of thetubular seal carrier. A suitable metal-to-metal seal means isillustrated at page 62 of the Baker Service Tools 1990 Catalog as the"Metal-To-Metal Tieback Stem."

One problem with the prior art devices has been possible damage to thesealmeans 21, 25, 27 during the running-in operation. The prior artdevices have typically utilized only the gauge ring 31 in order tocentralize the tubular seal carrier. The present device includes a guidemeans 45 locatedat the leading end of the seal carrier 23. In theposition shown in FIG. 1,the guide means 45 is in the fully expandedposition and closely fits within the surrounding cased well bore 15. Theguide means serves to centralize the seal carrier within the surroundingwell bore. As will be explained, the guide means is collapsible betweenan expanded, running-in position as shown in FIGS. 1 and 2 and aretracted position, shown in FIG.3, when positioned within thecooperating sealing bore of the polished sealbore receptacle 19.

FIG. 2 is a close-up view of one embodiment of the guide means 45 of theinvention. Again, the guide means 45 is located within the cased wellbore15 just prior to entering the polished bore surface of the polishedbore receptacle 19. The guide means includes a plurality of radiallymoveable guide dogs 47 which are located at the leading end 37 of thetubular seal carrier 23 within windows 49 located therein. As shown inFIGS. 2 and 3, the guide dogs 47 are radially shiftable between theexpanded position shown in FIG. 2 and the retracted position shown inFIG. 3 upon axial movement of the tubular seal carrier within thepolished seal bore surface19 of the casing bore receptacle. The guidedogs 47, as best seen in FIG. 2, are selectively sized to be closelyreceived within the surrounding interior of the cased well bore 15during the running-in operation. At least selected guide dogs 47 contactthe surrounding well bore 15 in orderto centralize the seal assemblywithin the cased well bore. The dogs are moved to the retracted positionshown in FIG. 3 upon contact with the upwardly facing shoulder 35 of thecasing bore receptacle.

In the embodiment of FIG. 2, the guide means 45 includes a spring loadedcollet 51 having a plurality of downwardly extending collet fingers 53.The collet is located within the leading end of the tubular seal carrier23 with the fingers thereof in contact with the guide dogs 47 forbiasing the guide dogs radially outward in the direction of the casedwell bore 15during the running-in operation. The collet fingers 53include lower extents 55 having inwardly slanting ramp surfaces 57 forcontacting a cooperating, oppositely arranged ramp surface 59 providedon each of the associated guide dogs 47. Each guide dog 47, in turn, hasan angled surface 61 for contacting the upwardly facing shoulder 35 ofthe casing bore receptacle 19. Contact between the angled surface 61 ofthe guide dog47 and the shoulder 35 causes inward movement of the guidedog and contact between the respective ramp surfaces 59, 57 of the guidedogs 47 and the collet fingers 55.

As shown in FIG. 3, such radial inward movement causes the upper extent63 of the guide dog 47 to pivot inwardly in the direction of an internalmandrel 65 which comprises a portion of the guide means 45. The recessedarea 67 provided between the upper and lower flanges 69, 71 of themandrel65 allow the guide dogs 47 to move to the retracted position asthe guide dog ramp surfaces 59 travel along the ramp surfaces 57 of thecollet 51. The lower flange 71 of the internal mandrel 65 includes aretaining shoulder 73 for engaging a lower extent 75 of the guide dog 47allowing pivotal movement of the guide dog lower extent 75 between theshoulder 73 and the internal surface of a nose ring 77. The nose ring 77has an externally threaded surface which, as shown in FIG. 3, engagesthe internally threaded surface 79 of the leading end 37 of the tubularseal carrier 23.

A coil spring 81 rests upon a shelf 83 formed by the upper flange 69.The coil spring 81 has an opposite end 85 which contacts the lower,internal surface 87 of the collet 51 in order to normally spring-biasthe collet upwardly as viewed in FIGS. 2 and 3. As shown in FIG. 2, thelower extents55 of the collet fingers are received within an internalgroove 89 providedwithin the leading end of the seal carrier 23 when inthe running-in position. Contact between the cooperating ramp surfaces57, 59 causes the collet fingers 53 to flex radially inward, allowingthe lower extents 55 to pop out of the associated groove 89. The coilspring 81 then spring-biases the fingers in the upward direction asviewed in FIG. 3 until the collet internal shoulder 82 contacts matingshoulder 84 of the internal mandrel 65. The internal mandrel 65 remainsstationary during thedescribed operation, being connected by means ofbolts 90 to the nose ring 77.

The collet 51 has a central bore 91 or orifice (FIG. 2) to allow thetransmission of fluids through the interior of the guide means. In orderto re-cock the mechanism, fluid is pumped from the well surface throughthe interior of the tubular seal carrier 23 and through the orifice 91into the interior (92 in FIG. 3) of the internal mandrel 65. A pressuredifferential of, e.g. 300 p.s.i., across the orifice 91 in the collettop plate 51 pushes the collet downwardly from the position shown inFIG. 3 tothe re-set, running-in position of FIG. 2.

The guide means can be formed of drillable materials, such as suitableplastics or soft metals, which can be drilled out of the interior of thetubular seal carrier 23 to provide an open bore within the seal carrierfor later operations. The guide means can also be engageable with aretrieving tool (not shown) for removal during later operations.

An invention has been provided with several advantages. The lead-inguide assembly is simple in design and economical to manufacture. Whenembodied as a seal assembly guide, the lead-in guide of the inventionprotects the more delicate tubing seals and prevents damage to the sealsduring the running-in operation. The device is simple in operation andextremely reliable. The device can also be re-cocked from the wellsurface by circulating fluid through the interior of the tubing string.

While the invention has been shown in only one of its forms, it is notthuslimited but is susceptible to various changes and modificationswithout departing from the spirit thereof.

What is claimed is:
 1. A seal assembly guide for centralizing a sealassembly being run from a well surface within a well bore to acooperating sealing bore located at a downhole location, the sealassembly guide comprising:a tubular seal carrier having abutting meansfor locating the seal carrier at a desired depth within the cooperatingsealing bore and having external seal means for establishing sealingintegrity with the cooperating sealing bore, the tubular seal carrierhaving a leading end and having a trailing end adapted to be made up ina tubing string leading to the well surface; collapsible guide meanslocated at the leading end of the tubular seal carrier for centralizingthe seal carrier within the surrounding well bore, the guide means beingcollapsible between an expanded, running-in position while above thesealing bore and a retracted position within the cooperating sealingbore; and wherein the abutment means comprises a downwardly facing no-goshoulder on the tubular seal carrier for engaging a cooperable upwardlyfacing shoulder provided as a part of the cooperating sealing borelocated at the downhole location.
 2. A seal assembly guide forcentralizing a seal assembly being run from a well surface within acased well bore to a cooperating sealing bore including a receptacleportion located at a downhole location, the seal assembly guidecomprising:a tubular seal carrier having abutting means for locating theseal carrier with respect to the receptacle portion of the cooperatingsealing bore and having external seal means for establishing sealingintegrity with the cooperating sealing bore, the tubular seal carrierhaving a leading end and having a trailing end adapted to be made up ina tubing string leading to the well surface; collapsible guide meanslocated at the leading end of the tubular seal carrier for centralizingthe seal carrier within the surrounding well casing as the tubular sealcarrier is being lowered from the well surface, the guide means beingcollapsible between an extended, running-in position while above thesealing bore and a retracted position within the cooperating sealingbore; wherein the receptacle portion of the cooperating sealing boredefines a polished seal bore surface and wherein the external seal meanson the tubular seal carrier establishes sealing integrity with thepolished seal bore surface when the tubular seal carrier is positionedwithin the cooperating sealing bore; and wherein the abutment meanscomprises a downwardly facing no-go shoulder on the tubular seal carrierfor engaging a cooperable upwardly facing shoulder on the receptacleportion of the sealing bore.
 3. The seal assembly of claim 2, whereinthe collapsible guide means includes a plurality of radially shiftableguide dogs located at the leading end of the tubular seal carrier, theguide dogs being radially shiftable between the expanded and retractedpositions upon axial movement of the tubular seal carrier within thereceptacle portion of the cooperating sealing bore.
 4. The seal assemblyof claim 3, wherein the guide dogs are selectively sized to be closelyreceived within the surrounding cased well bore during the running-inoperation at least selected dogs making contact with the well boreduring the running-in operation in order to centralize the seal assemblywithin the cased well bore and are moved to the retracted position uponcontact with the upwardly facing shoulder on the receptacle portion ofthe sealing bore.
 5. A seal assembly guide for centralizing a packoffseal assembly being run from a well surface within a cased well bore toa cooperating casing bore receptacle defining a polished seal boresurface located at a downhole location, the seal assembly guidecomprising:a tubular seal carrier having a downwardly facing shoulderfor locating the seal carrier with respect to a cooperable upwardlyfacing shoulder on the casing bore receptacle, the seal carrier havingexternal seal means for establishing sealing integrity with the polishedseal bore surface, the tubular seal carrier having a leading end andhaving a trailing end adapted to be made up in a tubing string leadingto the well surface; collapsible guide means located at the leading endof the tubular seal carrier for centralizing the seal carrier within thesurrounding cased well bore as the tubular seal carrier is being loweredfrom the well surface, the guide means being collapsible between anexpanded, running-in position while above the casing bore receptacle anda retracted position within the polished seal bore surface.
 6. The sealassembly guide of claim 5, wherein the collapsible guide means includesa plurality of radially movable guide dogs located at the leading end ofthe tubular seal carrier within window openings provided therein, theguide dogs being radially shiftable between the expanded and retractedpositions upon axial movement of the tubular seal carrier within thepolished seal bore surface of the casing bore receptacle.
 7. The sealassembly of claim 6, wherein the guide dogs are selectively sized to beclosely received within the surrounding cased well bore for contactingthe well bore during the running-in operation in order to centralize theseal assembly within the cased well bore and are moved to the retractedposition upon contact with the upwardly facing shoulder on the casingbore receptacle.
 8. The seal assembly of claim 7, wherein the guidemeans includes a collet having a plurality of collet fingers positionedwithin the leading end of the tubular seal carrier in contact withselected ones of the guide dogs for biasing the guide dogs radiallyoutward in the direction of the cased well bore during the running-inoperation, each of the collet fingers being provided with a ramp surfacefor contacting a cooperating ramp surface provided on the associatedguide dog, whereby contact of the guide dog with the upwardly facingshoulder of the casing bore receptacle allows inward movement of eachguide dog ramp surface along each collet finger ramp surface.
 9. Theseal assembly of claim 7, wherein the guide means is formed of adrillable material which can be drilled out of the interior of thetubular seal carrier to provide an open bore within the tubular sealcarrier during later operations.
 10. The seal assembly of claim 7,wherein the guide means is engageable with a retrieving tool forremovable during later operations.
 11. The seal assembly of claim 7,wherein the seal means includes at least one elastomeric ringcircumscribing the exterior of the tubular seal carrier.
 12. The sealassembly of claim 11, wherein the seal means includes at least onemetal-to-metal seal circumscribing the exterior of the tubular sealcarrier.